rust/src/libcore/ptr.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Unsafe pointer utility functions

#[forbid(deprecated_mode)];
#[forbid(deprecated_pattern)];

use cast;
use cmp::{Eq, Ord};
use libc;
use libc::{c_void, size_t};
use ptr;
use str;
use sys;
use vec;

#[nolink]
#[abi = "cdecl"]
extern mod libc_ {
    #[rust_stack]
    unsafe fn memmove(dest: *mut c_void,
                      src: *const c_void,
                      n: libc::size_t)
                   -> *c_void;

    #[rust_stack]
    unsafe fn memset(dest: *mut c_void,
                     c: libc::c_int,
                     len: libc::size_t)
                  -> *c_void;
}

#[abi = "rust-intrinsic"]
extern mod rusti {
    fn addr_of<T>(&&val: T) -> *T;
}

/// Get an unsafe pointer to a value
#[inline(always)]
pub pure fn addr_of<T>(val: &T) -> *T { unsafe { rusti::addr_of(*val) } }

/// Get an unsafe mut pointer to a value
#[inline(always)]
pub pure fn mut_addr_of<T>(val: &T) -> *mut T {
    unsafe {
        cast::reinterpret_cast(&rusti::addr_of(*val))
    }
}

/// Calculate the offset from a pointer
#[inline(always)]
pub pure fn offset<T>(ptr: *T, count: uint) -> *T {
    unsafe {
        (ptr as uint + count * sys::size_of::<T>()) as *T
    }
}

/// Calculate the offset from a const pointer
#[inline(always)]
pub pure fn const_offset<T>(ptr: *const T, count: uint) -> *const T {
    unsafe {
        (ptr as uint + count * sys::size_of::<T>()) as *T
    }
}

/// Calculate the offset from a mut pointer
#[inline(always)]
pub pure fn mut_offset<T>(ptr: *mut T, count: uint) -> *mut T {
    (ptr as uint + count * sys::size_of::<T>()) as *mut T
}

/// Return the offset of the first null pointer in `buf`.
#[inline(always)]
pub unsafe fn buf_len<T>(buf: **T) -> uint {
    position(buf, |i| *i == null())
}

/// Return the first offset `i` such that `f(buf[i]) == true`.
#[inline(always)]
pub unsafe fn position<T>(buf: *T, f: fn(&T) -> bool) -> uint {
    let mut i = 0;
    loop {
        if f(&(*offset(buf, i))) { return i; }
        else { i += 1; }
    }
}

/// Create an unsafe null pointer
#[inline(always)]
pub pure fn null<T>() -> *T { unsafe { cast::reinterpret_cast(&0u) } }

/// Create an unsafe mutable null pointer
#[inline(always)]
pub pure fn mut_null<T>() -> *mut T { unsafe { cast::reinterpret_cast(&0u) } }

/// Returns true if the pointer is equal to the null pointer.
#[inline(always)]
pub pure fn is_null<T>(ptr: *const T) -> bool { ptr == null() }

/// Returns true if the pointer is not equal to the null pointer.
#[inline(always)]
pub pure fn is_not_null<T>(ptr: *const T) -> bool { !is_null(ptr) }

/**
 * Copies data from one location to another
 *
 * Copies `count` elements (not bytes) from `src` to `dst`. The source
 * and destination may overlap.
 */
#[inline(always)]
pub unsafe fn copy_memory<T>(dst: *mut T, src: *const T, count: uint) {
    let n = count * sys::size_of::<T>();
    libc_::memmove(dst as *mut c_void, src as *c_void, n as size_t);
}

#[inline(always)]
pub unsafe fn set_memory<T>(dst: *mut T, c: int, count: uint) {
    let n = count * sys::size_of::<T>();
    libc_::memset(dst as *mut c_void, c as libc::c_int, n as size_t);
}

/**
  Transform a region pointer - &T - to an unsafe pointer - *T.
  This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub pure fn to_unsafe_ptr<T>(thing: &T) -> *T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Transform a const region pointer - &const T - to a const unsafe pointer -
  *const T. This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub pure fn to_const_unsafe_ptr<T>(thing: &const T) -> *const T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Transform a mutable region pointer - &mut T - to a mutable unsafe pointer -
  *mut T. This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.
*/
#[inline(always)]
pub pure fn to_mut_unsafe_ptr<T>(thing: &mut T) -> *mut T {
    unsafe { cast::reinterpret_cast(&thing) }
}

/**
  Cast a region pointer - &T - to a uint.
  This is safe, but is implemented with an unsafe block due to
  reinterpret_cast.

  (I couldn't think of a cutesy name for this one.)
*/
#[inline(always)]
pub pure fn to_uint<T>(thing: &T) -> uint {
    unsafe {
        cast::reinterpret_cast(&thing)
    }
}

/// Determine if two borrowed pointers point to the same thing.
#[inline(always)]
pub pure fn ref_eq<T>(thing: &a/T, other: &b/T) -> bool {
    to_uint(thing) == to_uint(other)
}

pub trait Ptr<T> {
    pure fn is_null() -> bool;
    pure fn is_not_null() -> bool;
    pure fn offset(count: uint) -> self;
}

/// Extension methods for immutable pointers
impl<T> *T: Ptr<T> {
    /// Returns true if the pointer is equal to the null pointer.
    #[inline(always)]
    pure fn is_null() -> bool { is_null(self) }

    /// Returns true if the pointer is not equal to the null pointer.
    #[inline(always)]
    pure fn is_not_null() -> bool { is_not_null(self) }

    /// Calculates the offset from a pointer.
    #[inline(always)]
    pure fn offset(count: uint) -> *T { offset(self, count) }
}

/// Extension methods for mutable pointers
impl<T> *mut T: Ptr<T> {
    /// Returns true if the pointer is equal to the null pointer.
    #[inline(always)]
    pure fn is_null() -> bool { is_null(self) }

    /// Returns true if the pointer is not equal to the null pointer.
    #[inline(always)]
    pure fn is_not_null() -> bool { is_not_null(self) }

    /// Calculates the offset from a mutable pointer.
    #[inline(always)]
    pure fn offset(count: uint) -> *mut T { mut_offset(self, count) }
}

// Equality for pointers
#[cfg(notest)]
impl<T> *const T : Eq {
    #[inline(always)]
    pure fn eq(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a == b;
        }
    }
    #[inline(always)]
    pure fn ne(&self, other: &*const T) -> bool { !(*self).eq(other) }
}

// Comparison for pointers
#[cfg(notest)]
impl<T> *const T : Ord {
    #[inline(always)]
    pure fn lt(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a < b;
        }
    }
    #[inline(always)]
    pure fn le(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a <= b;
        }
    }
    #[inline(always)]
    pure fn ge(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a >= b;
        }
    }
    #[inline(always)]
    pure fn gt(&self, other: &*const T) -> bool {
        unsafe {
            let a: uint = cast::reinterpret_cast(&(*self));
            let b: uint = cast::reinterpret_cast(&(*other));
            return a > b;
        }
    }
}

// Equality for region pointers
#[cfg(notest)]
impl<T:Eq> &const T : Eq {
    #[inline(always)]
    pure fn eq(&self, other: & &self/const T) -> bool {
        return *(*self) == *(*other);
    }
    #[inline(always)]
    pure fn ne(&self, other: & &self/const T) -> bool {
        return *(*self) != *(*other);
    }
}

// Comparison for region pointers
#[cfg(notest)]
impl<T:Ord> &const T : Ord {
    #[inline(always)]
    pure fn lt(&self, other: & &self/const T) -> bool {
        *(*self) < *(*other)
    }
    #[inline(always)]
    pure fn le(&self, other: & &self/const T) -> bool {
        *(*self) <= *(*other)
    }
    #[inline(always)]
    pure fn ge(&self, other: & &self/const T) -> bool {
        *(*self) >= *(*other)
    }
    #[inline(always)]
    pure fn gt(&self, other: & &self/const T) -> bool {
        *(*self) > *(*other)
    }
}

#[test]
pub fn test() {
    unsafe {
        struct Pair {mut fst: int, mut snd: int};
        let p = Pair {mut fst: 10, mut snd: 20};
        let pptr: *mut Pair = mut_addr_of(&p);
        let iptr: *mut int = cast::reinterpret_cast(&pptr);
        assert (*iptr == 10);;
        *iptr = 30;
        assert (*iptr == 30);
        assert (p.fst == 30);;

        *pptr = Pair {mut fst: 50, mut snd: 60};
        assert (*iptr == 50);
        assert (p.fst == 50);
        assert (p.snd == 60);

        let mut v0 = ~[32000u16, 32001u16, 32002u16];
        let mut v1 = ~[0u16, 0u16, 0u16];

        ptr::copy_memory(ptr::mut_offset(vec::raw::to_mut_ptr(v1), 1u),
                    ptr::offset(vec::raw::to_ptr(v0), 1u), 1u);
        assert (v1[0] == 0u16 && v1[1] == 32001u16 && v1[2] == 0u16);
        ptr::copy_memory(vec::raw::to_mut_ptr(v1),
                    ptr::offset(vec::raw::to_ptr(v0), 2u), 1u);
        assert (v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 0u16);
        ptr::copy_memory(ptr::mut_offset(vec::raw::to_mut_ptr(v1), 2u),
                    vec::raw::to_ptr(v0), 1u);
        assert (v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 32000u16);
    }
}

#[test]
pub fn test_position() {
    use str::as_c_str;
    use libc::c_char;

    let s = ~"hello";
    unsafe {
        assert 2u == as_c_str(s, |p| position(p, |c| *c == 'l' as c_char));
        assert 4u == as_c_str(s, |p| position(p, |c| *c == 'o' as c_char));
        assert 5u == as_c_str(s, |p| position(p, |c| *c == 0 as c_char));
    }
}

#[test]
pub fn test_buf_len() {
    let s0 = ~"hello";
    let s1 = ~"there";
    let s2 = ~"thing";
    do str::as_c_str(s0) |p0| {
        do str::as_c_str(s1) |p1| {
            do str::as_c_str(s2) |p2| {
                let v = ~[p0, p1, p2, null()];
                do vec::as_imm_buf(v) |vp, len| {
                    assert unsafe { buf_len(vp) } == 3u;
                    assert len == 4u;
                }
            }
        }
    }
}

#[test]
pub fn test_is_null() {
   let p: *int = ptr::null();
   assert p.is_null();
   assert !p.is_not_null();

   let q = ptr::offset(p, 1u);
   assert !q.is_null();
   assert q.is_not_null();

   let mp: *mut int = ptr::mut_null();
   assert mp.is_null();
   assert !mp.is_not_null();

   let mq = mp.offset(1u);
   assert !mq.is_null();
   assert mq.is_not_null();
}